There could be one hundred billion Earth-like planets in our galaxy, a US conference has heard.
Dr Alan Boss of the Carnegie Institution of Science said many of these worlds could be inhabited by simple lifeforms.
He was speaking at the annual meeting of the American Association for the Advancement of Science in Chicago.
So far, telescopes have been able to detect just over 300 planets outside our Solar System.
Very few of these would be capable of supporting life, however. Most are gas giants like our Jupiter; and many orbit so close to their parent stars that any microbes would have to survive roasting temperatures.
But, based on the limited numbers of planets found so far, Dr Boss has estimated that each Sun-like star has on average one "Earth-like" planet.
This simple calculation means there would be huge numbers capable of supporting life.
"Not only are they probably habitable but they probably are also going to be inhabited," Dr Boss told BBC News. "But I think that most likely the nearby 'Earths' are going to be inhabited with things which are perhaps more common to what Earth was like three or four billion years ago." That means bacterial lifeforms.
Dr Boss estimates that Nasa's Kepler mission, due for launch in March, should begin finding some of these Earth-like planets within the next few years.
Recent work at Edinburgh University tried to quantify how many intelligent civilisations might be out there. The research suggested there could be thousands of them.
It's common sense that there should be a fair few Earth-type planets in the galaxy, but one hundred billion? That's one for something like a third to a quarter of all the stars in the galaxy.
Only two things are infinite - the universe and human stupidity, and I'm not sure about the universe: Albert Einstein.
I hope we find one close to us really soon. Thats the type of discovery that will really inspire us to push space travel.
What does defeat mean to you?
Nothing it will never come. Death before defeat. I don’t bend or break. I end, if I meet a foe capable of it. Victory is in forcing the opponent to back down. I do not. There is no defeat.
That seems a bit high to me, to be honest. A third of all stars in the galaxy has an Earth like planet? Possible, I suppose, but still seems a bit far-fetched, IMHO.
Still, it'd be awesome if we found one with life on it.
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A huigely high estimate, I'd say. After discovering only 300 planetary masses, I don't think we have a large enough sample for that sort of statistical projection.
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I'll massacre your ass as fast
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Yeah that really goes beyond the old few tens of thousands to a million estimate. But then again these guys are smarter in the field of astronomy than I am. Pretty cool find
How many Minbari does it take to screw in a lightbulb?
None. They always surrender right before they finish the job and never tell you why.
It does seem a wee bit on the high side, and the sample is very small indeed. They also never defined exactly what is meant by "earth-like." The real earth is not just rocky, of a certain size and temperature, but has a magnetic field to repel solar winds, a large moon to stabilize the axis of rotation, a Jupiter to eject most space rocks from the inner system, etc. Lots and lots and lots of places could conceivably support very simple life - even places outside of earth in our solar system but complex and then intelligent life are further steps.
"If you can't take a little bloody nose, maybe you ought to go back home and crawl under your bed. It's not safe out here. It's wonderous, with treasures to satiate desires both subtle and gross... but it's not for the timid." Q, Q Who
It's common sense that there should be a fair few Earth-type planets in the galaxy, but one hundred billion? That's one for something like a third to a quarter of all the stars in the galaxy.
